Siemens Aktiengesellschaft

Axel Butterlin

Joachim Franke

Rudolf Kral

Frank Thomas

Hermann Dorr

The invention relates to a process for operating a continuous steam generator. The aim of the invention is to provide, with little technical complexity and for any operating state, a synchronous variation of the feed-water mass flow passing through the evaporator heating surface and of the heat input into the evaporator heating surface. To this end, a regulating device for the discharge of feed-water is allocated to a device for adjusting the feed-water mass flow. The control variable of said regulating device is the feed-water mass flow, while its set-point value in relation to the feed-water mass flow depends on the set-point value associated to the power of the steam generator. The actual value of the feed-water density at the entry of the pre-heater is fed to the regulating device for the discharge of feed-water as one of the input values.

Process for operating a continuous steam generator

A forced once-through steam generator with an evaporator heating surface has a control device for a furnace which is controlled by a setpoint value L assigned to the steam generator power and a control device for a feed-water mass flow M into the evaporator heating surface. In order to avoid an overshoot of a specific enthalpy at an outlet of the evaporator heating surface, a device is superimposed on the feedwater control device which serves to derive a variable Q(L1)/,[h.sub.sA (L2)-h.sub.iE) as a setpoint value M.sub.s for the feed-water mass flow. In this case h.sub.iE is the specific enthalpy at an inlet of the evaporator heating surface, Q(L1) is a value derived by a first power value L1 from a function generator for a heat flow into the evaporator heating surface and h.sub.sA (L2) is a setpoint value derived by a second power value L2 from the function generator for the specific enthalpy at the outlet of the evaporator heating surface. L1 is a first power value which is delayed with respect to the setpoint value L assigned to the steam generator power, and L2 is a second power value which is delayed with respect to the first power value L1.

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Bayreuth, Germany

Axel Butterlin